The present invention relates to a container for anaerobic products in particular anaerobic sealants and adhesives, in particular liquid products. Anaerobic adhesives and sealants cure, set-up or polymerise in the absence of oxygen (air).
The term anaerobic products as used here refers to formulations which cure, set-up or polymerise in the absence of air.
EP 0 352 143 describes an anaerobic liquid acylate sealant composition. U.S. Pat. No. 4,180 640 (Loctite) describes a hardenable adhesive and sealing composition. U.S. Pat. No. 3,218,305 (Krieble) discloses an anaerobic sealant composition. U.S. Pat. No. 2,895,950 and U.S. Pat. No. 3,046,262 (Krieble) also disclose anaerobic compositions. The products described in these specifications are examples of the type of product that may be stored in the container of the invention.
Containers or packages for storing anaerobic adhesive and sealant products are known. Typically such containers may be constructed from plastic, having substantially rigid walls, and capable of holding a number of liters of anaerobic product. Larger containers with pouring spouts are suitable only for low viscosity products. High viscosity products are not-easily decanted. It is known to provide semi-rigid plastic containers for such products. High viscosity products may be dispensed from containers by manual squeezing.
Rigid and semi-rigid containers are used with automatic dispensing machines. They do not readily conform to the shape of the dispenser and thus can create pockets of trapped (and therefore undispensing) products in the dispensing machine. High viscosity products tend to adhere to the walls of the container even if the container is pressurised, leaving a substantial amount of product within the container which is then wasted, or has otherwise to be removed from the container. A further disadvantage of such containers is the shelf life of products and particularly of anaerobic products placed in such containers if the container is filled beyond a certain level. Containers for anaerobic products are ordinarily left with a headspace above the level of liquid in the container. Typically 30% to 60% of the internal volume of the container is left unfilled with anaerobic product, depending on the rigidity of the side wall of the container in order to give a sufficient shelf-life. This allows a sufficient volume of air (oxygen) to remain within the container to help stabilise the anaerobic product. There exists however a conflict between the necessity to seal in the product on the one hand and to allow air (oxygen) to permeate through the product on the other. Such containers when filled or nearly full do not provide commercially acceptable shelf life for anaerobic products, as there is not sufficient air (oxygen) present in the container, nor does sufficient air permeate into the container. There is therefore substantial wastage of packaging materials and higher costs due to the partial filling of containers with this product.
Containers made from air-permeable material allow air through their walls etc. This air may replace air in the headspace or may permeate into the product within the container. However in order to ensure stability of anaerobic products permeation into the headspace alone is not sufficient to ensure adequate shelf-life. The air must permeate through the product also to ensure curing, setting up or polymerisation of the product does not occur. The area where curing, setting up or polymerisation is most likely to first occur is at the centre of the mass of product. Thus even with an air permeable container, and headspace of air in the container, curing or setting up or polymerisation may take place prematurely giving the product a shorter than desired shelf-life. The problem of curing or setting up is exacerbated by elevated storage temperatures. It is known to refrigerate, for example at temperatures of 2-8xc2x0 C., certain anaerobic products which are sensitive to polymerisation, curing or setting up (particularly those of high viscosity) in order to prevent premature curing. Temperatures greater than about 28-30xc2x0 C. cause even more rapid curing or setting up of anaerobic products.
An example of one of such containers is commonly referred to as a xe2x80x9ccubitainerxe2x80x9d [commercially available from Dynopack Ltd. in the U.K.]. The name stems from its cubic shape. The container is constructed from a typically translucent plastic constructed from low density polyethylene/ethylene vinyl acetate (LLDPE/EVA) copolymer mixed with linear low density polyethylene (LLDPE) with a wall thickness of about 160 xcexcm to 180 xcexcm. A nozzle with a threaded cap is fitted at the centre of the top wall of the container. Typically the cubitainer has a 3 liter internal volume, which is used to hold 1 liter or 2 liters, of an anaerobic adhesive. The less anaerobic adhesive placed in the cubitainer the greater the shelf-life of the adhesive.
The cubitainer has a continuous welded seam which runs about the outside of the container. The seam runs along one side of the base wall, then diagonally across a first side wall, then across one side of the top wall and then diagonally down a second side wall opposite the first side wall to meet the base wall to form a continuous seam about the container.
The container is relatively rigid, though its contents can be dispensed manually by squeezing the walls of the container to some extent. However, users of the cubitainer have noticed that substantial amounts of medium to high viscosity product remain in the container despite manual pressure, causing them to resort to cutting open the container to remove the contents. The cubitainer is packaged within an external paperboard carton which prevents physical damage to the plastic walls and allows stacking. The oxygen permeability of the cubitainer at 20xc2x0 C. and 350 xcexcm wall thickness is about (546 cm3/m2.day.atm) 553 cm3/m2.day.bar.
When partially full the cubitainer provides a storage means for anaerobic containers which gives the product an excellent shelf life. However as stated above partially filled containers are wasteful of materials and energy. It is of course possible to fill the cubitainer completely, but in practice it has not been filled as this would compromise the shelf-life of the product. Furthermore the cubitainer is suitable only for low to medium viscosity products, not for medium to high viscosity products due to their xe2x80x9cdifficult to pourxe2x80x9d nature. High viscosity products have been traditionally sold in xe2x80x9cbucket with lidxe2x80x9d containers i.e. a very wide mouthed container (and thus large) to allow the product to be removed manually from the container.
The containers described above are all xe2x80x9cstand-alonexe2x80x9d containers i.e. the rigidity of the side-walls is sufficient to allow the container to stand without falling over or deforming to any appreciable extent under internal pressure from its contents. To make a stand-alone container it is necessary to conform to a base area:height ratio which makes the container stable when standing. The cubitainer described above is packaged in a paperboard carton to protect it from damage during transport, storage and the like. The cubitainer is a stand-alone container, its cubic shape and relatively rigid side walls allowing it to stand on its base.
Another form of container used for high viscosity anaerobic products is a cartridge having a nozzle and a built-in piston from which product is dispensed by a dispensing gun etc. No headspace is left in the cartridge. This severely limits the shelf-life of the product. Furthermore the amounts placed in these cartridges are relatively small, of the order of 300 ml to 800 ml. Larger volumes would result in an even shorter shelf-life of the product.
A collapsible container is known from EP-A-0172711 which is suitable for use with medicaments or other liquids which must be preserved from contamination. Likewise EP-A-0590465 relates to a composite film barrier for packaging oxygen-sensitive products. These containers are intended to prevent the ingress of air into the interior of the container and therefore would not be suitable for use with anaerobic products which would cure or polymerise in the absence of air (oxygen).
Composite films for bag-in-box-type containers are known from JP-A-07 701 002-A (see Derwent Abstract: Accession No. 95-182607 [24]). Such films are made from outer layers of ultra-low density polyethylene or linear low density polyethylene with an intermediate gas barrier layer. The gas barrier layer may be of polyamide resin layer, saponified ethylene-vinyl acetate copolymer layer and polyamide resin layer or alternatively of polyamide resin layer, polyolefin adhesive resin layer and saponified ethylene-vinyl acetate copolymer layer. The outer and intermediate layers are bonded by adhesive resin. The films are described as having good gas barrier properties and are thus useful for storing food products and chemicals.
Similar products are known from U.S. Pat. No. 4,863,770, U.S. Pat. No. 4,851,272 and U.S. Pat. No. 4,778,699 and all are considered to have good oxygen or gas permeation barriers.
Anaerobic products in the types of container described above have been available commercially for some time. There therefore exists a need to provide a container for anaerobic products which:
(i) confers excellent shelf life stability on anaerobic products;
(ii) may be used to store any one of low, medium or high viscosity products while allowing the product to be dispensed manually or to be dispensed automatically from a dispensing apparatus, without difficulty, and which may be filled to a level where the headspace in the container is minimised; and
(iii) prevents the anaerobic product from escaping from the container, but does not exclude air by permeation into the container i.e. does not provide a substantial barrier to the permeation of air.
A minimal headspace typically does not exceed the volume of the nozzle/cap. However it will be appreciated that achieving a headspace of less than 20% of the container would be a significant improvement over prior art containers, when the shelf-life of the product is not compromised by the minimal headspace.
The present invention provides a flexible container for anaerobic products comprising at least one wall defining a cavity for receiving and retaining an anaerobic product, the wall being made of a deformable, oxygen permeable material, such that the container is sufficiently flexible to substantially conform to the shape of a further container into which it may be placed.
The flexible container may be made of a thin layer or layers of an oxygen-permeable material such as polyethylene or polypropylene and formed in the shape of a bag. Suitable materials are linear low density polyethylene, very low density polyethylene, high density polyethylene or polypropylene or blends, co-extrusions or laminates of these products. The flexible container may comprise two or more layers of oxygen permeable material. The wall thickness may be at least 50 xcexcm and the permeability of a wall is suitably 25 cm3/m2.day.bar or greater. The flexible container may be opaque. This is desired where the product is light sensitive.
In another aspect, the invention provides a pack which comprises a flexible and a rigid container. The flexible container may be provided in an outer substantially rigid oxygen permeable container which can hold the flexible container and can retain the flexible container in use in a predetermined shape when containing anaerobic product. The outer container retains the flexible container in its optimum position for allowing oxygen to permeate through to the anaerobic product. This gives an excellent shelf-life while the container in which the adhesive is stored is flexible and allows products to be dispensed easily. The product may be decanted or dispensed irrespective of its viscosity.
A low viscosity anaerobic product contained within the flexible container may be dispensed without removing the flexible container from the outer container if the outer carton is so adapted. In particular the flexible container may be provided with a nozzle which may be opened or closed to dispense the contents of the flexible container.
In one aspect of the invention, the flexible container comprises a plastic bag and the outer container comprises a substantially rigid carton. The carton may comprise paperboard and may be of a flattened or flatpack shape. In other words, one dimension of the pack may be substantially less than the other two dimensions e.g. the width and depth may be greater than the height. Suitably, in use, the outer container retains the flexible container when containing a mass of anaerobic product to a shape in which the distance from any point in the product to a wall is less than or equal to 4 cm.